Macro photography refers to taking pictures of small objects at a close distance (such as a distance within approximately 30 cm) by a photographic device. In recent years, applications of macro photography are extended from ecological photography of animals and plants to high-magnification visual inspection and non-destructive inspection required in manufacturing processes of industrial products.
In the field of macro photography, the illumination for an object is relatively more important than general photography. In earlier times, a ring flashlight installed on the front of a lens was unable to provide continuous illuminations, and just provided synchronous light at the moment of taking a picture, so that a user couldn't make sure whether or not an object had received exact light from the flash light before taking the picture, and the user generally had to adjust the aperture and shutter speed of a camera based on the user's past experience, and thus a relatively high failure rate of taking pictures would result.
Recently, most ring lights adopt cold cathode fluorescent lamp (CCFL) or light emitting diode (LED) as a light source. Although the required continuous illumination is provided for previewing an object before a picture is taken, yet the object has a non-uniform brightness with a darker center and a brighter periphery if the ring light is very close to the object while the picture is being taken.
Furthermore, the ring light is annularly projected onto the object, but its projection angle is completely symmetric and unvarying. Thus the object illuminated by the ring light will have few shadows. In other words, the profile and details of the object can be illuminated clearly, but it may look not like a stereoscopic one.